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1.
Protosporangium is described as a new genus of the mycetozoan order Protosteliida, with 3 new species: P. bisporum, P. fragile , and P. articulatum . The genus is characterized by minute, mostly 2-4-spored sporangia borne on long, slender, flexuous stalks. The spores produce flagellate cells (typically 8 per sporangium) during germination. The trophic stage is holozoic and uninucleate to plurinucleate but never reticulate. Plurinucleate protoplasts segment into uninucleate (sometimes binucleate) prespore cells that culminate to form sporocarps in the manner characteristic of protostelids. 相似文献
2.
Karen A. Steidinger JoAnn M. Burkholder Howard B. Glasgow Cecil W. Hobbs Julie K. Garrett Earnest W. Truby Edward J. Noga Stephen A. Smith 《Journal of phycology》1996,32(1):157-164
The newly described toxic dinoflagellate Pfiesteria piscicida is a polymorphic and multiphasic species with flagellated, amoeboid, and cyst stages. The species is structurally a heterotroph; however, the flagellated stages can have cleptochloroplasts in large food vacuoles and can temporarily function as mixotrophs. The flagellated stage has a typical mesokaryotic nucleus, and the theca is composed of four membranes, two of which are vesicular and contain thin plates arranged in a Kofoidian series of Po, cp, X, 4′, 1a, 5″, 6c, 4s, 5″′, and 2″″. The plate tabulation is unlike that of any other armored dinoflagellate. Nodules often demark the suture lines underneath the outer membrane, but fixation protocols can influence the detection of plates. Amoeboid benthic stages can be filose to lobose, are thecate, and have a reticulate or spiculate appearance. Amoeboid stages have a eukaryotic nuclear profile and are phagocytic. Cyst stages include a small spherical stage with a honeycomb, reticulate surface and possibly another stage that is elongate and oval to spherical with chrysophyte-like scales that can have long bracts. The species is placed in a new family, Pfiesteriaceae, and the order Dinamoebales is emended. 相似文献
3.
芡实花粉败育的细胞学观察 总被引:4,自引:0,他引:4
芡实(EuryaleferoxSalisb.)花粉的败育主要发生在小孢子母细胞减数分裂时期和小孢子单核期与二核期。形成的不正常四分体中有一些具有不完整的横隔壁,一些则完全不形成横隔壁,而发育成具4个核的原生质团;气候异常是造成该时期不育现象的主要原因之一。小孢子单核期及二核期存在发育异常的孢子。绒毡层的提前发育、过早解体、肥大生长及延迟退化是花粉败育的一个重要原因。 相似文献
4.
Two new taxa of Liagoraceae (Nemaliales) are described from Western Australia. Gloiotrichus fractalis gen. et sp. nov. has been collected from 3–20 m depths at the Houtman Abrolhos, Western Australia. Plants are calcified, extremely lubricous, and grow to 17 cm in length. Carpogonial branches are straight, 6 or 7 cells in length, arise from the basal or lower cells of cortical fascicles, and are occasionally compound. Branched sterile filaments of narrow elongate cells arise on the lower cells of the carpogonial branch prior to gonimoblast initiation, at first on the basal cells, then on progressively more distal cells. Following presumed fertilisation the carpogonium divides transversely, with both cells giving rise to gonimoblast filaments. The distal cells of the carpogonial branch then begin to fuse, with fusion progressing proximally until most of the cells of the carpogonial branch are included. As fusion extends, the filaments on the carpogonial branch are reduced to the basal 2 or 3 cells. The gonimoblast is compact and bears terminal carposporangia. Spermatangial clusters arise on subterminal cells of the cortex, eventually displacing the terminal cells. The sequence of pre- and post-fertilisation events occurring in the new genus separates it from all others included in the Liagoraceae, although it appears to have close affinities with the uncalcified genus Nemalion. Ganonema helminthaxis sp. nov. was collected from 12 m depths at Rottnest Island, Western Australia. Plants are uncalcified and mucilaginous, the axes consisting of a few (< 10) primary medullary filaments, each cell of which gives rise to a cortical fascicle at alternate forks of the pseudodichotomies borne on successive medullary cells. Subsidiary (adventitious) filaments and rhizoids comprise the bulk of the thallus. Carpogonial branches are straight, (3-)4(-6) cells in length, arise on the basal 1–4 cells of the cortical fascicles, and are frequently compound. Carposporophytes develop from the upper of two daughter cells formed by a transverse division of the fertilised carpogonium. Ascending and descending sterile filaments girdle the carpogonial branch cells and arise mostly on the supporting cell prior to fertilisation. Ganonema helminthaxis is the first completely non-calcified member of the genus, and its reproductive and vegetative morphology supports the recognition of Ganonema as a genus independent from Liagora. Liagora codii Womersley is a southern Australian species displaying features of Ganonema, to which it is transferred. 相似文献
5.
记述龙蝎蛉新科Drakonochoristidae fam. nov.和1新亚科及其2新属、种和1个老亚科。2新属种的化石标本采自中国陕西铜川中三叠统铜川组下段上部的灰绿色泥岩和页岩。新科性质及其分类位置在文中进行讨论。新科的建立填补这个类群在中国的空白,同时对于小蝎蛉科Nannochoristidae和二叠蝎蛉科Permochoristidae的演化关系的研究有一定的意义。这些新属、种系陕西昆虫群(陕西生物群的一个类别)铜川昆虫组合的新成员。铜川组的时代相当于欧洲拉丁尼期(Ladinian Stage)。 相似文献
6.
Cryptonemia specimens collected in Bermuda over the past two decades were analysed using gene sequences encoding the large subunit of the nuclear ribosomal DNA and the large subunit of RuBisCO as genetic markers to elucidate their phylogenetic positions. They were additionally subjected to morphological assessment and compared with historical collections from the islands. Six species are presently found in the flora including C. bermudensis comb. nov., based on Halymenia bermudensis, and the following five new species: C. abyssalis, C. antricola, C. atrocostalis, C. lacunicola and C. perparva. Of the eight species known in the western Atlantic flora prior to this study, none is found in Bermuda. Specimens reported in the islands in the 1900s attributed to C. crenulata and C. luxurians are representative of the new species, C. antricola and C. atrocostalis, respectively. 相似文献
7.
Two new propagule-farming red algae from southern Australia, Deucalion levringii (Lindauer) gen. et comb. nov. and Anisoschizus propaguli gen. et sp. nov., are described and defined largely on their development in laboratory culture. Deucalion is included in the tribe Compsothamnieae on the basis of its subapical procarp and alternate distichous branching. It differs from the other genera included in that tribe in that it produces 3-celled propagules, polysporangia, a subapical cell of the fertile axis which bears 3 pericentral cells, and an apparently post-fertilization involucre which develops from the hypogenous and sub-hypogenous cells of the fertile axis. Its gametophyte morphology has been elucidated in culture, as only sporophytes are known from the field. Gametophytes do not appear to produce propagules. Anisoschizus is provisionally included in the tribe Spermothamnieae on the basis of its subdichotomous branching, possession of a prostrate system and the production of polysporangia. It differs from the other genera of the tribe in the production of 2-celled propagules. Observations on the germination of the “monosporangia” of Mazoyerella arachnoidea and Monosporus spp. indicate that they are analagous to the propagules of Deucalion and Anisoschizus. The nature of these propagules and their role in recycling the parent plant are discussed and contrasted with true monosporangia. It is recommended that Monosporus be maintained as a form genus containing representatives from more than one tribe, as exemplified by plants from Lord Howe I. provisionally identified as M. indicus Boergesen which have both prostrate and erect, as opposed to only erect, axes. 相似文献
8.
辣椒雄性不育材料H9A小孢子败育机理 总被引:1,自引:0,他引:1
运用光学、电子显微技术及生化指标测定法, 对辣椒(Capsicum annuum)雄性不育材料H9A及其保持系H9B小孢子不同发育时期进行细胞形态学观察及生化特性分析。结果表明, 雄性不育材料H9A的小孢子败育发生在单核前期, 由于绒毡层细胞极度膨胀, 四分体受挤压后破裂并降解, 无法形成正常的单核花粉粒, 属于孢子体败育。不育材料花蕾中的过氧化物酶活性从四分体时期开始明显高于保持系, 保持系游离脯氨酸含量从单核小孢子期开始明显高于不育材料; 不育材料小孢子发育各时期的可溶性蛋白含量都明显低于保持系, 但丙二醛含量均高于保持系。 相似文献
9.
Asteromenia gen. nov. (Rhodymeniales, Rhodophyta) is proposed with a single species, Asteromenia peltata (W. R. Taylor) comb. nov. (basionym: Fauchea peltata W. R. Taylor). Thalli of the proposed new genus are stipitate with dorsiventral, peltate blades that are initially circular in shape but with age become stellate with ligulate arms. Internally, the blades have a polystromatic medulla of large, hyaline cells, grading into a cortex of smaller, pigmented cells. Clusters of translucent cells occur on the dorsal surface of the blade. Tetrasporangia are formed by transformations of intercalary midcortical cells. Mature tetrasporangia have cruciately arranged spores and are densely aggregated in the cortex, mostly on the ventral surface, but occasional tetrasporangia also arise on the dorsal surface. Carpogonial branches are four-celled and arise on inner cortical cells. Auxiliary cells are borne on auxiliary mother cells attached to supporting cells of the carpogonial branches. Cystocarps are protuberant, with well-developed, ostiolate pericarps that often have extended, proboscis-like necks. The new genus differs from the previously described peltate or dorsiventral taxa in the Rhodymeniaceae by its polystromatic medulla (Maripelta and Sciadophycus have a monostromatic medulla), intercalary tetrasporangia formed in an unmodified cortex, and four-celled carpogonial branches (Halichrysis, as typified by H. depressa (J. Agardh) F. Schmitz, has terminal tetrasporangia in nemathecia and three-celled carpogonial branches). 相似文献
10.
Pihiella liagoraciphila gen. et sp. nov. (Rhodophyta) is described for a minute endo/epiphyte that is commonly associated with members of the Liagoraceae ( Nemaliales, Rhodophyta). Algae are discoid or subspherical and grow to a maximum diameter of 400 μm. Attachment is via isolated elongate rhizoids that penetrate into the loosely filamentous structure of the host or by a pad of several coalesced rhizoids where the host has a more cohesive cortex. Elongate surface hairs are common. Gametophytes are dioecious, the spermatangia arising on surface cells, and carpogonia with elongate trichogynes borne directly on undifferentiated surface supporting cells. Large sporangia form on stalk cells across the upper surface of the plants, these appearing to be either monosporangial or the result of fertilization of the carpogonia and equivalent to undivided zygotosporangia. Carposporophytes and tetrasporangia are unknown. 18S rRNA gene sequence analyses indicate that Pihiella constitutes a clade of long branch length most closely related to the Ahnfeltiales. The unique morphology and reproduction of Pihiella , combined with a substantial genetic divergence from the Ahnfeltiales, suggest that it is sufficiently distinct to warrant placement in a new family and order. We therefore describe the family Pihiellaceae and the order Pihiellales to accommodate the new genus. 相似文献
11.
I. A. Bryantseva V. M. Gorlenko T. P. Tourova B. B. Kuznetsov A. M. Lysenko S. A. Bykova V. F. Gal’chenko L. L. Mityushina G. A. Osipov 《Microbiology》2000,69(3):325-334
Two new species of heliobacteria isolated from cyanobacterial mats of two alkaline sulfidic hot springs are formally described.
Strains BR4 and BG29 are assigned to anoxygenic phototrophic bacteria of the familyHeliobacteriaceae, since they possess the unique properties of this taxon: strict anaerobiosis, formation of bacteriochlorophyllg, the lack of extensive intracytoplasmic membranes and chlorosomes, an unusual cell wall structure, and phylogenetic relatedness
to the low G+C gram-positive eubacteria. Based on the 16S rDNA sequence similarity, strains BR4 and BG29 are assigned to the
genusHeliobacterium and described as two new species of this genus:Heliobacterium sulfidophilum sp. nov. andHeliobacterium undosum sp. nov. The G+C content of the DNA is 51.3 mol % inHbt. sulfidophilum and 57.2-57.7 mol % inHbt. undosum. The cells ofHbt. sulfidophilum are rods, and the cells ofHbt. undosum are slightly twisted spirilla or short rods. Both new bacteria are motile by peritrichous flagella.Hbt. sulfidophilum produces endospores. The new bacteria are strict anaerobes growing photoheterotrophically on a limited range of organic compounds.
In the dark, they can switch from photosynthesis to the slow fermentation of pyruvate. Biotin is required as a growth factor.
Both species are highly tolerant to sulfide (up to 2 mM at pH 7.5) and oxidize it photoheterotrophically to elemental sulfur;
photoautotrophic growth was not observed. The temperature optimal for growth ofHbt. sulfidophilum andHbt undosum is 30–35‡C, and the optimal pH is 7–8. 相似文献
12.
The flower develops in March and blossoms in early May in Nanjing. The
cytokinesis of microsporocytes is simultaneous and most tetrads are tetrahedral. The tapetum
is secretory and the nuclei become polyploid at last. The style is solid and most ovaries are
unilocular, rarely bilocular. The ovule is pendulous, anatropous and unitegmic. The nucellus is
pseudocrassinucellate. An obturator formed by transmitting tissue covers the micropyle. The
raphe vascular strand extends into the integument when it reaches the chalaza and on a whole
keeps a “U” shape. The endothelium cell is uninucleate. In most cases no nucellar cap is
formed. No hypostase is found below the embryo sac. The archesporium is one-celled. The
embryo sac development conforms to the Polygonum or Allium types. The degeneration of
the megaspores in the linear tetrad usually occurs from the chalazal toward the micropylar
end. Two synergids persist during fertilization. Three antipodal cells are uninucleate and
ephemeral. Two polar nuclei fuse at the time of fertilization. The fertilization type accords
with porogamy. The syngamy is premitotic. The development of endosperm is cellular.
The initial four successive divisions of the primary endosperm cell are transverse-verticaltransverse-transverse subsequently, giving rise to sixteen cells of the early endosperm. The
mature embryo is straight and nearly as long as the endospermous seed. The cotyledons are
more or less cordate at base. The seedoat is thin and composed of 5-11 layers of compressed
cells. Neither embryo nor endosperm contain the alkaloid camptothecine.
The major similarities of Nyssa sinensis to the American nyssas in embryology, which
may be a counted as the generic features, are the polyploid tapetum cells, the unitegmic ovule
with U-shaped vascular strand, the direct enlargement of the archesporial cell to produce the
megasporocyte, the pseudocrassinucellus, the usual absence of the nucellar cap, the
Polygonum or Allium type of the embryo sac development, the first degeneration of the
metachalazal megaspore, the ephemeral antipodal cells, a single nucleolus in the nucleus ofthe primary endosperm cell, the more or less cordate base of the cotyledons. 相似文献
13.
A new species, Bosmina tripurae is described from South India. The species shares some of the morphological traits with Bosmina
fatalis from East and SE Asia, and two other species described recently from North America. They all form a subgeneric group
established earlier: subgenus Sinobosmina Lieder 1957. Parthenogenetic females of the new species are superficially similar
to the species Bosmina longirostris, which occurs on Indian subcontinent, only in northern high mountain lakes. All reports
of the latter species from Indian lowlands are either Bosmina tripurae or some other not yet described species.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
14.
Sugita T Takashima M Poonwan N Mekha N Malaithao K Thungmuthasawat B Prasarn S Luangsook P Kudo T 《Microbiology and immunology》2003,47(3):183-190
The genus Pseudozyma is ustilaginomycetous anamorphic yeasts, and are mainly isolated from plants. We isolated three Pseudozyma strains from the blood of patients in Thailand. While one isolate was identified as P. antarctica by rDNA sequence analysis, the other two were considered to be new species and were named P. parantarctica and P. thailandica. The three isolates proved to be resistant to 5-flucytosine, and P. thailandica was also resistant to fluconazole and itraconazole. As far as we know, this is the first isolation of Pseudozyma strains from humans. The two new species are described. 相似文献
15.
A new ceramiaceous alga, Sciurothamnion stegengae De Clerck et Kraft, gen. et sp. nov., is described from the western Indian Ocean and the Philippines. Sciurothamnion appears related to the tribe Callithamnieae on the basis of the position and composition of its procarps and by the majority of post‐fertilization events. It differs, however, from all current members of the tribe by the presence of two periaxial cells bearing determinate laterals per axial cell. Additionally, unlike any present representative of the subfamily Callithamnioideae, no intercalary foot cell is formed after diploidization of the paired auxiliary cells. The genus is characterized by a terminal foot cell (“disposal cell”), which segregates the haploid nuclei of the diploidized auxiliary cell from the diploid zygote nucleus. The nature of three types of foot cells reported in the Ceramiaceae (intercalary foot cells containing only haploid nuclei, intercalary foot cells containing haploid nuclei and a diploid nucleus, and terminal foot cells containing only haploid nuclei) is discussed. 相似文献
16.
jvind Moestrup 《Journal of phycology》1991,27(1):119-133
The tiny jumping flagellate originally described as Pedinomonas mikron Throndsen was isolated into pure culture from Australian waters and its ultrastructure critically examined. Pedinomonas mikron differs in behavior and in features of the flagellar apparatus from P. minor, the type species from freshwater, and is referred to the new genus Resultor. The two genera are closely related and form the new class Pedinophyceae, which is characterized by features of the flagellar apparatus, mitosis, and cytokinesis. The flagella show the 11/5 orientation otherwise characteristic of Ulvophyceae and Pleurastrophyceae, but they are arranged end to end as in the Chlorophyceae. The flagellar root system is asymmetric and includes a rhizoplast that emerges from the base of one flagellum but subsequently associates with a microtubular root from the second basal body. Mitosis studied previously by Pickett-Heaps and Ott in Pedinomonas is closed, unlike in other green algae, and the spindle is persistent. No phycoplast or phragmoplast is formed during cytokinesis. The eyespot of the Pedinophyceae is located at the opposite end of the cell from the flagella and adjacent to the pyrenoid, as in the most primitive members of the Prasinophyceae. Members of the Pedinophyceae lack prasinoxanthin and Mg 2,4D, characteristic of certain other primitive green algae. The primitive green algae include the classes Prasinophyceae and Pedinophyceae. Micromonadophyceae Mattox et Stewart is considered a synonym of Prasinophyceae. Two new orders are established, Pedinomonadales, containing all known members of the Pedinophyceae, and Scourfieldiales, with the single family Scourfieldiaceae fam. nov. and the single genus Scourfieldia. 相似文献
17.
Karen A. Steidinger Jan H. Landsberg Patrice L. Mason Wolfgang K. Vogelbein Patricia A. Tester R. Wayne Litaker 《Journal of phycology》2006,42(4):951-961
A new genus and species of heterotrophic dinoflagellate, Cryptoperidiniopsis brodyi gen. et sp. nov., are described. This new species commonly occurs in estuaries from Florida to Maryland, and is often associated with Pfiesteria piscicida Steidinger et Burkholder, Pseudopfiesteria shumwayae (Glasgow et Burkholder) Litaker et al., and Karlodinium veneficum (Ballantine) J. Larsen, as well as other small (<20 μm) heterotrophic and mixotrophic dinoflagellates. C. brodyi gen. et sp. nov. feeds myzocytotically on pigmented microalgae and other microorganisms. The genus and species have the enhanced Kofoidian plate formula of Po, cp, X, 5′, 0a, 6″, 6c, PC, 5+s, 5″′, 0p, and 2″″ and are assigned to the order Peridiniales and the family Pfiesteriaceae. Because the Pfiesteriaceae comprise small species and are difficult to differentiate by light microscopy, C. brodyi gen. et sp. nov. can be easily misidentified. 相似文献
18.
Akiko Yokoyama Joseph L. Scott Giuseppe C. Zuccarello Makiko Kajikawa Yoshiaki Hara John A. West 《Phycological Research》2009,57(4):278-289
A new unicellular red alga, Corynoplastis japonica gen. et sp. nov., is described from Tobishima, Japan. Cells are spherical, 18–33 µm in diameter, pale purple to brownish red and surrounded by a mucilaginous sheath. A single chloroplast with many lobes extends from the cell periphery to the cell center. A peripheral thylakoid is present. A pyrenoid occurs at each innermost chloroplast lobe end and one or two thylakoids are present in the pyrenoid matrix. The nucleus is eccentric to peripheral and Golgi bodies are scattered throughout the cell and associated with endoplasmic reticulum. Cells have a slow random gliding motility. The low molecular weight carbohydrate mannitol is present in the cells. Molecular phylogenetic analysis indicates that this alga is closely related to members of the genus Rhodella. A new order, Dixoniellales, is established for Dixoniella, Neorhodella and Glaucosphaera based on molecular and ultrastructural evidence (Golgi bodies associated only with the nucleus). The redefined order Rhodellales in which Rhodella and Corynoplastis are placed is characterized ultrastructurally by Golgi bodies scattered throughout the cytoplasm and associated with endoplasmic reticulum. 相似文献
19.
Kenneth H. Nicholls 《Journal of phycology》1990,26(3):558-563
The life cycle of a previously undescribed chrysophyte, assigned to the new genus Rhizoochromonas, is described. It includes a small motile stage with heterokont flagellation which invades a Dinobryon lorica. Reproduction by cell division of the nearly spherical rhizopodial vegetative stage frequently leads to expulsion of the host protoplast through overcrowding of the lorica. Endogenous cysts (stomatocysts) are also formed within the Dinobryon lorica. The new family, Brehmiellaceae, is established to accommodate pseudopodial/rhizopodial chrysophytes with heterokont flagellation in the motile stage. Rhizoochromonas endoloricata gen. et sp. nov. has been found at two widely separated softwater locations in Ontario, and at one it constituted a major component of the planktonic flora during the autumns of six successive years. 相似文献
20.
Gerald T. Kraft Gary W. Saunders Isabella A. Abbott Ricardo J. Haroun 《Journal of phycology》2004,40(2):383-394
An encrusting brown alga from subtidal habitats around the island of Oahu (Hawaiian Islands) represents only the second genus of the class Phaeophyceae to form calcium carbonate, which it deposits primarily as both extracellular and intracellular aragonite, admixed with small (3.3%) amounts of calcite. Plants form expanses 15–100+ cm in extent consisting of horizontally aligned imbricating tiers of distromatic blades 1–4 mm in diameter that are separated from one another by cementing layers of extracellular aragonite, the tiers forming stacks of dozens of laminae and anchored to coral substrata by a basement layer that adheres tightly without haptera or rhizoids. The hypodermal layer of each blade consists of lightly pigmented rectilinear cells bearing either one or two smaller deeply pigmented epidermal cells in cross‐sectional profiles and three or four in long‐sectional profiles, the cells of both layers becoming encased in rigid carbonate skeletons laid down in their outer wall matrices. The successive tiers become stacked by either overgrowing marginal proliferations or new blade primordia that arise from the hypodermal layer of surface laminae and initially spread centrifugally by means of continuous marginal meristems. Neither plurilocular nor unilocular reproductive structures are known. The alga is described as the new genus and species Newhousia imbricata Kraft, G.W. Saunders, Abbott et Haroun and is assigned on the basis of small subunit rDNA gene sequence analyses to the order Dictyotales, family Dictyotaceae, within a strongly supported monophyletic clade that includes Distromium, Lobophora, and Zonaria. 相似文献